The leaders of Germany, France, Ukraine and Russia discussed the shaky cease-fire in eastern Ukraine in a four-way telephone conversation Thursday.

The office of German Chancellor Angela Merkel said the four leaders agreed that the "fragile" cease-fire needs to be "stabilized," and that the political process that started with the cease-fire agreements signed in February should be intensified by setting up working groups.

The office of French President Francois Hollande said violations of the cease-fire and fighting, particularly near the southeastern port city of Mariupol, the village of Shyrokyne, which is near Mariupol, the Luhansk region town of Schastye and the Donetsk airport, must stop. Monitors with the Organization for Security and Cooperation in Europe reported observing intense fighting Sunday near Shyrokyne.

Ukrainian military spokesman Andriy Lysenko said Thursday that one serviceman was killed and another four wounded over the previous 24 hours.

According to the office of Ukrainian President Petro Poroshenko, the four leaders called for "strict observance" of the cease-fire agreement and stressed that the OSCE must have access to points along the "line of contact" between Ukrainian government and Russia-backed separatist forces in order to monitor the cease-fire.

The Ukrainian president's office also said that during the phone call, President Vladimir Putin "agreed with the possibility of stationing a peacekeeping contingent" in eastern Ukraine.

In February, Poroshenko called for an international peacekeeping mission for his country, saying an EU "police mission" would be the best option. He repeated the appeal Monday during a meeting with EU officials, calling for "the deployment of a European Union operation" to help establish "the proper security conditions" for fulfilling the cease-fire agreement.

EU President Donald Tusk responded that the bloc will send a civilian "assessment" mission to explore ways to assist Ukraine, but that it would be "impossible" to send a "military mission.”

The Kremlin said in a statement about Thursday's four-way phone call that the four leaders noted "certain progress on the issues of ensuring a cease-fire and the withdrawal of heavy weapons from the conflict zone." However, it made no mention of Putin agreeing to the possibility of deploying peacekeepers to eastern Ukraine.